Since frictions in a support mechanism for a precise positioning table have great influence on the mobility capability, a drive apparatus that minimizes friction forces in the supporting mechanism is normally used.
Meanwhile, there has been a minute moving device that actively utilizes frictions acting on frictional sliding surfaces and can perform precise positioning of submicron order, though the moving device has a small-sized, simple mechanism. This moving device is a minute moving device that takes advantage of electromagnetic repulsion forces and rapid deformation of piezoelectric elements, and has a so-called “impact mechanism.” The impact mechanism has a small-sized, simple structure and is capable of making minute step movements. In view of this advantage, precise positioning tables, micromanipulators, and the like have been suggested.
Further, various applications have already been suggested by taking advantage of the phenomenon that friction forces become smaller through generation of high-frequency microvibrations, and such a phenomenon is also utilized in some positioning devices. For example, drive apparatuses that take advantage of a friction reducing effect by using ultrasonic vibrations have been known.
However, a today's precise positioning table is required not only to achieve a simple objective such as higher precision or higher speed, but also to achieve higher speed, higher stabilizability, higher stability, and more precise positioning in a single drive apparatus, and to realize each of the objectives at even higher levels.
As mentioned above, a drive system that minimizes friction forces in the supporting mechanism unit is often used. Most of such drive systems are designed to use hydrostatic air bearings. Such drive systems exhibit excellent characteristics in precise positioning, but do not satisfy the requirements in terms of speed, stabilizability, and stability. Further, such drive apparatuses are large in size, and are expensive.
Having a small-sized, simple structure, an impact mechanism is a small-sized device and is inexpensive. With the use of an impact mechanism, it is possible to produce a precise positioning system having an extremely high precision. Such an impact mechanism also exhibits excellent characteristics in stabilizability and stability. However, because of its drive principles, an impact mechanism makes minute step movements, and therefore, is not satisfactory in terms of speed.
By reducing frictions in the bearing mechanism with the use of ultrasonic vibrations, excellent precise positioning is performed by taking advantage of a friction reducing effect, and high stabilizability and high stability are achieved by taking advantage of a frictional sliding effect. However, no specific measures have been suggested to improve the speed that is adversely affected by the frictional sliding effect. Therefore, there has been demand for development of specific structures and drive methods to solve the problem.